The present invention relates generally to improvements in fuel cell fuel delivery arrangements for use in combustion tools, and more specifically to adapters provided to combustion tool fuel cells for obtaining more consistent fuel dosing.
In the present application the term “combustion tool” refers to combustion powered fastener driving tools, also known as combustion nailers, cordless framing tools, cordless trim tools and the like. More particularly, the present invention relates to improvements in the delivery of fuel from fuel cells customarily provided for such purposes.
Such tools typically have a housing substantially enclosing a combustion power source, a fuel cell, a battery, a trigger mechanism and a magazine storing a supply of fasteners for sequential driving. The power source includes a reciprocating driver blade which separates a forward most fastener from the magazine and drives it through a nosepiece into the workpiece. Exemplary tools are described in U.S. Pat. Nos. 4,483,473; 4,522,162; 6,145,724; and 6,679,414, all of which are incorporated by reference. Such fastener-driving tools and such fuel cells are available commercially from ITW-Paslode (a division of Illinois Tool Works, Inc.) of Vernon Hills, Ill., under its IMPULSE trademark.
As exemplified in Nikolich U.S. Pat. Nos. 4,403,722; 4,483,474; and 5,115,944, all of which are also incorporated by reference, it is known to use a dispenser such as a fuel cell to dispense a hydrocarbon fuel to a combustion tool. A design criterion of such fuel cells is that only a desired amount of fuel or dose of fuel should be emitted by the fuel cell for each combustion event. The amount of fuel should be carefully monitored to provide the desired combustion, yet in a fuel-efficient manner to prolong the working life of the fuel cell.
Prior attempts to address this dosage factor have resulted in fuel metering valves located in the tool (U.S. Pat. No. 5,263,439) or attached to the fuel cell (U.S. Pat. No. 6,302,297), both of which are also incorporated by reference. Fuel cells have been introduced having internal metering valves, as disclosed in U.S. Pat. No. 7,392,922, also incorporated by reference.
Regardless of the location of the metering valve, the associated combustion nailer is designed to exert a force on the valve, either the reciprocating valve stem or on the valve body itself, to cause the stem to retract against a biasing force in the metering valve to dispense a measured dose of fuel. It is important for fuel economy in the fuel cell, and for desired operation of the combustion nailer, for only the designated amount of fuel to be supplied to the tool on a dosage basis.
However, variations in manufacturing tolerances often result in a tolerance “stack up” which under some circumstances can interfere with the designed connection between the fuel cell and the tool, as well as the fuel actuation mechanism of the tool, which depresses the fuel cell valve stem before each combustion cycle to obtain the desired fuel dosage for combustion. Thus, there is a need for a combustion tool which provides for consistent fuel delivery while accommodating the tolerance stack up inherent in combustion tool manufacturing.